1. Field of the Invention
The present invention relates to a substrate treatment apparatus to treat a substrate with a treatment liquid, to which ultrasonic waves are applied.
2. Description of the Related Art
Processes for manufacturing a semiconductor device or liquid crystal display device include a lithography process to form a circuit pattern on a substrate, such as a semiconductor wafer or a glass substrate. The lithography process, as well known, includes a series of steps of applying a resist to the substrate, irradiating the resist with light via a mask on which a circuit pattern is formed, removing a part of the resist which is not irradiated with light (or a part of the resist which is irradiated with light), and etching a part from which the resist is removed. The above steps are repeated a plurality of times, so that a circuit pattern is formed on the substrate.
In the series of steps described above, if the substrate is soiled, the circuit pattern cannot be precisely formed, resulting in production of a defective item. Therefore, when forming a circuit pattern in each step, the substrate is treated with a treatment liquid to bring the substrate to a clean state in which no resist or minute particles, such as dust, may remain.
A spinning apparatus is known as the abovementioned apparatus that treats a substrate with a treatment liquid. The spinning apparatus has a cup body. A turntable is provided in the cup body. The substrate is removably held on the turntable.
A nozzle body is disposed above the turntable. A treatment liquid is supplied to the substrate from the nozzle body while the turntable is rotating, thereby treating the substrate.
There is a possibility that soil adhering to a substrate cannot be fully removed simply by supplying a treatment liquid to the substrate. Therefore, ultrasonic vibrations are applied to the treatment liquid to be supplied to the substrate, so that the cleaning efficiency can be improved.
Conventionally, the nozzle body is used to supply an ultrasonically vibrated treatment liquid to a substrate. The nozzle body has a supply port and a spray port for the liquid, and contains a vibration plate. The treatment liquid is supplied to the nozzle body through the supply port, brought into contact with the vibration plate which is ultrasonically vibrated, accelerated at the spray port which has a small opening area, and sprayed on the substrate.
The treatment liquid sprayed on the substrate is repeatedly pressurized and depressurized by ultrasonic vibrations. In the depressurizing time, a void is formed around gas as a core, which has been dissolved in the liquid. In the pressurizing time, the void collapses, resulting in generation of a shock wave, which is called cavitation. As a result, the soil is removed from the substrate.
It is known that the cavitation, which results from application of ultrasonic vibrations to the treatment liquid, is more significant as the temperature of the treatment liquid is higher. However, if the cavitation in the treatment liquid is significant, fine wirings formed on the substrate may be damaged by the cavitation. Therefore, when ultrasonic vibrations are to be applied to the treatment liquid, it is required to control the temperature of the treatment liquid.
Besides, the conventional nozzle body has a structure in which, the treatment liquid is brought into contact with the vibration plate provided inside the nozzle body, so that ultrasonic vibrations are generated, as described above. The vibration plate, which is ultrasonically vibrated is heated by the energy applied to the vibration plate to a high temperature. Therefore, the temperature of the treatment liquid, which is brought into contact with the vibration plate, inevitably increases.
Accordingly, when the substrate is treated with the ultrasonically vibrated treatment liquid, the substrate may be damaged.
Moreover, the treatment liquid sprayed from the spray port of the nozzle body on the substrate is accelerated. The accelerated treatment liquid applies shock to the substrate, which may also damage the substrate.